Gear Vendor and MPG

[b737jets]

Okay guys who runs the Gear Vendor overdrive... I have a new 04. 5 and needed the 4. 10 to tow my 5'ver. I also use this truck to drive 210 miles R/T daily to work all at Hwy. speed. I need some mpg help and real numbers to work from.



Who has the G/V unit installed & what are you getting... ...



I get 17. 7 at 65 & 15. 8 at 70... ..... w/o the G/V... ..... the truck is still breaking in though. My 02 HO got 20. 8 at 70 & 21. 6 at 65 I'm looking to get back closer to those numbers if possible. ( all these number are empty )



I drive apprx 52K per year and at today fuel prices even 1. 5 mpg increase would pay off in 3 years







any info would be great

 

[Mopar_Mudder]

This has been discussed many times, do a search for it.



Boils down to that you have to put on 250,000-300,000 miles for the gear vendor unit to pay for itself in milage.



So in my opinion it isn't even close to worth it.

 

[b737jets]

I know it was ... ... ..... it has many topics



I looked through them all more the most part and found no one was giving exact numbers or I just didnt see it after going blind looking at my screen for several hrs.

 

[Doubleclutch]

Mopar Mudder- you might need to grease up the abacus. With the price of fuel over $2. 00, it doesn't take as many miles.

Hey flyboy those are some good numbers on what you had, and what you have. My 3. 73 geared 4x4 is getting about 17. 7 with the 6 spd. Still working on that second thousand miles. The '96 truck with the 3. 54 and 5 spd. has a GV unit in it. Haven't seen much of a mpg improvment, but I got the puppy for gear splitting, because of the gaps between the gears. 5th over is about 93mph @ 2000 rpm. Do some number crunching to determine your engine rpm at different gears w/wo GV overdrive. I'm told that keeping less than ~2000 rpm will keep milage good.

Greg

 

[Sherman]

mph

Originally posted by Mopar_Mudder

This has been discussed many times, do a search for it.



Boils down to that you have to put on 250,000-300,000 miles for the gear vendor unit to pay for itself in milage.



So in my opinion it isn't even close to worth it.

At $2. 00 per gallon and and improvement of 3mi/gal the pay back is $923. per 20,000mi. ,at $1. 75 /gallonand the same improvement the pay back is $808. per 20,000 miles. PAY ME NOW OR PAY ME LATER!!!!!!!

 

[John - K5AWO]

I just did a quick little spreadsheet to see how this would effect me. This is how it played out.





Fuel at $2. 09 per gallon avg

Gear Vendor estimate_____________Cost/Mile___Cost/yr 20k miles

Current MPG at 60 mph_______16_____0. 13_____$2612

Hoped for improvement_______19_____0. 11_____$2200

Gain (lucky toss of coin)_______3_____0. 02_____$412___<--Savings/yr



Cost of Gear Vendor unit

$2,695. 00______________130,667___<-- Miles required to break even.



Obviously, if the mpg improvement fell short of 3 mpg, this scenario would have a lot of holes in it fast.



I made the break even computation by dividing the Gear Vendor cost by the savings per mile accurate to six places. I only showed two places for display.



This means I would have to keep my 6 year old truck another 6 years before I could even break even on the cost of the unit. The up side though would be my 2000 rpm economy cruise just might get me a few extra MPH before wind resistance took too heavy of a toll.



Now if I made my living traveling a lot of miles, this would be shortened IF the load was light enough to pull in OD. I doubt that would ever be the case, most likely the improvement would only be realized when dead heading.



I think the hoped for improvement previously mentioned of $900+ for 20,000 is optimistic IMO.



Can someone tell me how to make this web site display TABS correctly?? I had to space everything out with those underscore characters.





John

 

[John - K5AWO]

The previous scenario tells me that the only way to make this thing work is to order the truck with real tall gears and then use the Gear Vendor as Under Drive to help get a load moving or crawling up big hills.



I think the six speed box is the only way to go and forget the OD/UD unit.

 

[klenger]

Having owned a truck with 3. 54's, 4. 10's and now 3. 73's, I can assure you that you will never see anything close to a 3 MPG gain.

 

[b737jets]

Since this is a new truck I think the return on the investment would work if the unit provides an improvement in mpg. Thats why I was wondering for those who have this G/V unit installed what are they getting or if anyone knows of someone who has the G/V unit and what they seeing as far as mpg.



I don't mind doing 60 to 65 to keep the mpg up.



However in L. A. traffic it can be a little hairy with folks riding your butt pushin ya to go faster even in the slow lane.



So with that said I would even be happy if I could cruise at 70 and hold my current mpg of 18. 3 at 63 mph. ( which seems to be the sweet spot ) My 02 HO 4x4 would get 20. 8 at 70 mph producing approx 2000 rpm.



I just don't like to look down and see 2300 rpm at 70 and a 15. 1 mpg.



The numbers that I worked out were close to the post above me, I figure it would take an extra year but those are some good calculations.



I figured with G/V 6th over ratio that it would produce a 1779 rpm at 70mph give or take a few rpm. That makes a difference of 499 rpm +/- a few rpm. which would make smile a little and make the cummins purr a little nicer. I know that these engines are built handle the higher rpm range but with a reduction of nearly 500 rpm the engine and components have just that much less wear.



So there you have it..... I know folks will say why did ya get it with 4. 10's but the deal I got for my trade and the price they sold me the new truck at... ... was a no brainer... ... .



With all that said I'm just looking to make an informed decision



any information would be great.

 

[John - K5AWO]

Originally posted by klenger

Having owned a truck with 3. 54's, 4. 10's and now 3. 73's, I can assure you that you will never see anything close to a 3 MPG gain.

Dampersville



I didn't think so, but it sure is easy to look at that 27% ratio in the OD unit and try to apply that to street mpg improvement.



Guess the ole adage, fuel=speed*power*load just can't be got around any way you cut it. (formula a gimmick for effect)



Just for the sake of argument, since you have had all three gear ratios klenger, what has been the range of mpg values for say, 60 mph?

 

[klenger]

01. 5 with 3. 54's would top out at about 20 MPG. I only had that truck for 10,000 miles.



01. 5 with 4. 10's would top out at about 19 MPG. I had it for 35,000 miles.



04. 5 with 3. 73's get's about 17. 5 average, but have seen close to 19 MPG.



If much of your driving is around town, the milage with 4. 10's is no worse than lower ratios because you can get into the highest gear faster. I am convincenced that gear ratios have much less to to with milage than driving habits, speed, weight, tire pressure, 4WD, auto transmission, etc. YMMV (literally).

 

[John - K5AWO]

Originally posted by klenger

I am convincenced that gear ratios have much less to to with milage than driving habits, speed, weight, tire pressure, 4WD, auto transmission, etc. YMMV (literally).

Thanks for the input on the mpg vs gearing. And yes, most of my driving is in town.



Going to work is 2 miles with 4 lights, 14 miles of freeway and then 2 miles of 40 mph and 1 light plus two positive stops.



Back home is worse: Go home parking lot precludes the freeway (costly way- start/stop every 75 feet).



So, I just drive tail-end charlie and try to catch as many lights as I can using the side streets going home. Usually I can get by with only 8 or 9 stops and average something like 35 mph with some 2 mile stretches of 50-55.



I agree with your statement on the 4. 10s and getting to top gear quicker. I let it roll out to about 10 mph and the 1-2 upshift, then just a tad of torque to get up to 35-36 so the OD will click in when I ease off just a smidgen. Then cruise in OD at 38-43 most of the way home except for those 2 stretches of 2 miles between lights.



So far, over six months, I have averaged 16. 0 city/highway driving. Lately I have been limiting myself to 2000 rpm tops so see how much that helps. up until last week, if the traffic was doing 80, so did I. Not anymore. $2. 27 put an end to that.



Up until now, I have carried 45 psi in all the tires because of the rough ride. I am thinking about bumping up the front tires to 70-80 and monitor the tread temps with my IR gun and see if the tread pattern is flat on the ground. Right now, it is obvious the outside edges are getting too much scuffing.

 

[Matt400]

Originally posted by b737jets

any info would be great,

__________________

04. 5 Q-cab silver dually Laramie 4. 10

Is yours a 2wd or 4wd? Maybe another avenue would be to increase tire size. .

If it doesn't cause trouble with your trailer (height wise) you could go big enough to see 2000 rpm @70 in OD.

When towing, lock out OD for increased rpm's and power.



You can play around with some different size tires here



Using the bottom chart plug in 1. 0 for drive with converter locked and . 69 for OD with converter locked, that will show what the rpm’s will be in those gears based on your 4. 10’s and what ever size tires you select.

 

[Sherman]

Re: mph

Originally posted by Sherman

At $2. 00 per gallon and and improvement of 3mi/gal the pay back is $923. per 20,000mi. ,at $1. 75 /gallonand the same improvement the pay back is $808. per 20,000 miles. PAY ME NOW OR PAY ME LATER!!!!!!!

My #'s are based on 10miles per gal and 13miles per galfor comparison,which at $2. 00 per gal yields $923. I get 10 miles per gal when towing at 2300 rpm at 70mph, when I drop back to 1850 rpm my mileage goes up to 13 mpg,a US Gear aux box would give that spread in overdrive,the guestion is how much windage is reduced by the lower speed, I bet 1/2 to 1 mpg with a net cruise gain of 2 to 21/2 mpg,using 2mpg increase at cruise it would take 80,000mi to pay for a US Gear box,fro the highway hauler it works, for a weekend warrior it gets ifffffy!

 

[klenger]

Sherman:



As a rule of tuumb, wind resistance (and horse power) increases at a rate that is the square of the increase in speed. In your example, reducing your speed from 70 mph to 56 mph reduces the HP required by about 35% solely from the reduction in wind resistance. If you were to try to tow at 70 MPH at 1850 RPM, the engine would be totally out of it's power band and unable to supply the power required to maintain that speed, assuming anything close to a stock engine setup.

 

[RustyJC]

You should be aware that you cannot use an exhaust brake while the Gear Vendor unit is engaged - it cannot handle the reverse power application. Generally speaking, the Gear Vendor unit works best with automatics, while the U. S. Gear unit works best with manual transmissions.



Rusty

 

[Sherman]

Cummins

Originally posted by klenger

Sherman:



As a rule of tuumb, wind resistance (and horse power) increases at a rate that is the square of the increase in speed. In your example, reducing your speed from 70 mph to 56 mph reduces the HP required by about 35% solely from the reduction in wind resistance. If you were to try to tow at 70 MPH at 1850 RPM, the engine would be totally out of it's power band and unable to supply the power required to maintain that speed, assuming anything close to a stock engine setup.

Cummins tells me that max torque is at 1600 rpm,1800rpm will work all day long,as far as drag, you have to be more specific on what is being towed,a sheet of plywood 4x8 would create more drag than a pencil, the CD{coificient of drag} is what is important,35% of nothing is still nothing. The question now is: can the Cummins provide the the required power at 1850rpm,Cummins says yes!What do you say?

 

[klenger]

While max torque may be at 1600, max HP doesn't happen to much higher. It requires more HP to tow at 70 MPH than it does at 56 MPH, even though the torque may be the same.

 

[b737jets]

In response to Matt 500



I have thought about a tire change to accomplish the aspect of reduction in rpm to cruise faster. Matt the cost of installing 6 new tires and rims will be 2/3 rd to 3/4 the cost of the G/V and since the truck is new it makes no sense to do that change... .....



I know i could probably sell the rims and tires to recoup some of the cost but I guess I will just have to wait and see what direction I will take... ... ...



by the way I'm 2wd

 

[AQuaglieri]

I was thinking about a GV unit, but the cost is a little high. I'm thinking about going for larger tires like 315/70/17. I think th GV unit is 22% overdrive. The tire change from 265/70/17 to 315's would be about a 10% overdrive. I would go from 4. 10 to 3. 77 rear gears. And it would be a lot cheaper.